Boot for recovery
purposes - Used to boot the system when a damaged file or file system is preventing
the system from booting. You might need to do one or both of the following
to boot for recovery purposes:

SPARC: Using the Boot PROM

System administrators typically use the PROM level to boot a system.
Occasionally, however, you might need to change the way the system boots.
For example, you might want to reset the device to boot from or run hardware
diagnostics before you bring the system to a multiuser level.

SPARC: How to Change the Default Boot Device

You might need to identify the devices on the system before you can
change the default boot device to some other device. For information on identifying
devices on the system, see SPARC: How to Identify Devices on a System.

SPARC: How to Reset the System

Run the reset command from the ok
prompt.

ok reset

This self-test program, which runs diagnostic tests on the hardware,
is executed and the system is rebooted.

SPARC: Booting a System

If a system is turned off, turning it on starts the multiuser boot sequence.
The following procedures show how to boot to different run levels from the ok PROM prompt. These procedures assume that the system has been
cleanly shut down, unless stated otherwise.

SPARC: How to Boot a System From the Network

Any system can boot from the network
if there is a boot server available. You might want to boot a standalone system
from the network temporarily if the system cannot boot from the local disk.
For information on changing or resetting the default boot device, see SPARC: How to Change the Default Boot Device.

Two network configuration boot strategies are available on sun4u systems:

If both methods are available, you can specify which service to use
in the boot command temporarily. Or, you can save the network
boot strategy across system reboots at the PROM level, by setting up an NVRAM
alias. The following example uses the nvalias command to
set up a network device alias for booting DHCP by default on a Sun Ultra 10
system.

ok nvalias net /pci@1f,4000/network@1,1:dhcp

This alias means that when you type boot net, the
system boots by using the DHCP network book strategy.

Caution –

You should not use the nvalias command to
modify the NVRAMRC file unless you are very familiar
with the syntax of this command and the nvunalias command.
For information on using these commands, see the OpenBoot 3.x Command
Reference Manual.

If necessary, shut down the system.

Determine the method for booting from the network and select one of
the following:

You must have already set up a RARP or DHCP boot server in your network
to use either method to boot successfully.

Boot the system from the network by using the DHCP method.

ok boot net[:dhcp]

If you have changed the PROM setting to boot DHCP by default, as in
the preceding nvalias example, you only have to specify boot net.

Boot the system from the network by using the RARP method.

ok boot net[:rarp]

Since RARP is the default network boot strategy, you only have to specify boot net:rarp if you have changed the PROM value to boot DHCP.

SPARC: How to Stop the System for Recovery Purposes

Type the stop key sequence for your system.

The monitor displays the ok PROM prompt.

ok

The specific stop key sequence depends on your keyboard type. For example,
you can press Stop-A or L1-A. On terminals, press the Break key.

Synchronize the file systems.

ok sync

When you see the syncing file systems... message,
press the stop key sequence for your system again.

SPARC: Example—Booting a System if You Forgot Root Password

The following example shows how to recover when you forget the root
password by booting from the network. This example assumes that the network
boot server is already available. Be sure to apply a new root password after
the system has rebooted.